Antenna



Jan. 5,1937. 'Q EHM ET AL 2,066,874

` ANTENNA Filed Oct. 30, 1933 *E @HT l n l I f@ E i ATTORNEY PatentedJan. 5, 1937 ANTENNA Otto Bhm, Albrecht Gothe, and Hans Otto ROOS,-

enstein, Berlin, Germany, assignors to Telefunken Gesellschaft frDrahtlose Telegraphie m. b. H., Berlin, Germany, a corporation ofGermany Application October 30, 1933, Serial No. 695,734

In Germany October 31, 1932 5 Claims.

` In operating with medium and long waves (above 100 In.) only theground radiation can be utilized for safe transmission. The spaceradiation either becomes lost or causes disturbing fading phenomena,when they are reflected by the Heaviside l-ayer. Therefore, attemptshave been made for a long time to construct antenna with reduced spaceradiation. Theoretically this can be achieved by means of very highantennas. Practically, antennas have been constructed the height ofwhich is of the order of one half wave length and in which radiation issuppressed below a definite angle of elevation. However, thissuppression has only been effective for some angles, but not for alarger range of angles.

'I'he greatest, economically operating antenna height is held to beabout 200 1n. Thus, for broadcasting waves between 200 and 550 m. it is1A to 036k, where A is the symbol for wave length. In accordance withthepresent invention for antenna heights equal to or less than one wavelength, vertical diagrams are effected which, practically speaking, donot produce radiation within a l-arge range of angles. This isaccomplished by subdividing the antenna into several parts, which arearranged to radiate alternately at opposite phase. Each antenna of theheight of one half wave length is made to be constructed from at leastthree such parts radiating in opposite phase. Where the antenna heightis greater than one half wave length, any sector of the antenna of M2length is to be composed of at least three parts radiating alternatelyat opposite phase.

The length of the individual radiating parts, their height above ground,and their current amplitudes are variable and are designed for eachindividual case in such manner that the desired vertical diagram isfullled to the fullest extent. If, for instance, an antenna height of%7\ is prescribed, and if it is intended to suppress as far as possiblethe radiation within an angle range between and 90 from the horizontal,this can, for instance, be attained by the following arrangement:

The entire antenna height according to the invention is divided intothree equal parts of M8 each; the lower and upper part are fed -at equalphase and at equal amplitude J: the

middle part is fed at opposite phase and at an amplitude being `1.55 aslarge (see Figure l). Thus a vertical diagram is obtained with thegreatest eld intensity in the horizontal direction. In the angle rangebetween 55 and 90 angle the (Cl. Z50-33) field intensity is at the most3% of the maximum intensity. f

Figure 1 shows, by way of example only, an

antenna in accordance with'the present `invention. VFigure 2 ismerely'given byway of com-` parison to show the current distribution ina straight linear antenna of a particular height, Figure 3 representsgraphically field intensity and angle of rise for both Figures 1 and 2;and Figures 4 and 5 show modifications of the arrangement oi Figure l.

More specifically, Figure 3 shows a graphical representation of thevertical diagram of the 'antenna arrangement (curve I) in rectangularcoordinates. In the abscissa axis the angles of rise from the horizontalare plotted and the ordinate shows the relative field intensities. Forthe purpose of comparison'there is also shown the diagram V(curve II) ofan antenna of in height with the ordinary, current distribution (Figure2) (current node at the top). Both di-agrams are reduced to the samehorizontal iield intensity. In the first diagram (curve I) the 'eldintensity is lower than 3% maximum field intensity only between the riseangles 57-90.

It is obvious that the above example is not the only solution of theproblem to be considered, but represents only an example of particularsimplicity. By varying the length of the individual radiating parts aswell as their amplitude relations, diagrams can be obtained solving theproblem in consideration even better.

'Ihe single radiating parts may be individually fed by energy lines. Acommon feed may also be provided at the bottom of the antenna, as shownin Figure 4. In this case the predetermined current distribution isobtained by suitable dimensioning of self-inductance and capacity of theindividual radiating parts. The self-inductance can be changed in regardto a straight wire for instance in winding this wire into a coil. Thelatter arrangement has the advantage that the current distribution alongthe antenna can be changed by varying the pitch of the wire turnswhereby the desired current distribution is obtained, as shown in Figure5. In this way the self-inductance ofthe conductor is primarily changed.In order to vary the capacity the diameter of the coil may, forinstance,

be changed or in case of a straight antenna the same may be formed asbow net aerial.

Due to the separate variation of self-inductance and capacity it ispossible to shorten the length of the conductor as may be desired sothat in one sector of one half wave length threeV parts) radiatingalternately at opposite phase can be produced. The shortening of thelength can also be produced in another manner. ior instance, in formingthe antenna Wire of zigzag shape. In this case the attainable shorteningof the length is dependent upon the length of the wire provided for adenite antenna length.

We claim:

1. A vertical antenna having a section 'not exceeding one-half wavelength and which section has at least three parts, and means for causingalternate parts to radiate in phase and adjacent parts out of phase.

2. 'Ihe combination with a Vertical antenna having a. physical heightless than one-half the' length of the communication wave, said antennaconstituting at least three radiating sections, of means for causingalternate sections to radiate in phase and adjacent sections out ofphase.

3. A vertical antenna having a physical height less than one-half thelength of the communication wave, said antenna comprising threeradiating sections one above the other, means for supplying theuppermost .and lowermost of said three radiating sections with currentsof equal amplitude and the middle section With current of greateramplitude.

4. A vertical antenna having a physical height less than one-half thelength of the communication Wave, said antenna comprising threeradiating sections one above the other, means for supplying theuppermost and lowermost of said three radiating sections With currentsof equal phase and amplitude and the middle section with current whichis out of phase with said rst mentioned currents and of greateramplitude.

5. A vertical antenna having a section not substantially exceedingone-half wave length and. which section comprises three radiatingsefions one abovef-the other, means for supplying the c jj'most y 'idlowermost of said three radiating sections with currents of equal phaseand amplitude and the middle section with current which is out of phasewith said first mentioned currents and of greater amplitude.

oTTo BHM.

ALBRECHT GOTHE. HANS OTTO ROOSENSTEIN.

